This is true. BenQ (even with original, unpatched firmware) is very good at writing media at higher than its rated speed. I also appreciate its ability to write RICOHJPNR01 and TYG01 at 8x and 12x with good quality (after MediaCodeSpeedEdit). As far as I know, nobody came up with a way to overspeed media on LG drives. The only official overspeed I've encountered so far with GSA-4163B is YUDEN000T02 at 12x Z-CLV, which translates into 6:30-6:40 burn time, thanks to its 10000 RPM.
However, since my primary goal was to compare writing quality, I must note that BenQ writing quality does not improve with lower speeds on the media I've presented above... at least, I haven't noticed any significant differences in BenQ writing quality between 8x and 12x on CMCMAGAE1, ProdiscF01, TYG02, or YUDEN000T02. (See the scans below.)
What would LG GSA-4163B produce at 12x on 8x rated media we may never know... unless LG becomes interested in including these speeds in its firmware, or somebody finds a way to decode and patch LG firmware. Based on LG performance on MCC004, I would guess that it would have no problem writing good media at 1.5-2x rated speed, but, again, LG didn't give us any means to test that
Here are some more BenQ scans to illustrate my point that its writing quality does not change much from lowering burn speed to what each media is rated at.
1st pair of scans: CMCMAGAE1, 8x on the left, 12x on the right.
2nd pair of scans: ProdiscF01, 8x on the left, 12x on the right.
3rd pair of scans: TYG02, 8x on the left, 16x on the right.
4th pair of scans: YUDEN000T02, 8x on the left, 12x on the right.